Brachial cuff

• US 9,314,170 B2
• Filed: 05/05/2011
• Issued: 04/19/2016
• Est. Priority Date: 05/07/2010
• Status: Active Grant

• Current Assignee: Atcor Medical Pty Ltd (CardieX Ltd.)
• Original Assignee: Atcor Medical Pty Ltd (CardieX Ltd.)
• Inventors: Qasem, Ahmad M.
• Primary Examiner(s): Cheng, Jacqueline
• Assistant Examiner(s): TOTH, KAREN E
• Application Number:
  US13/101,193
• Publication Number:
  US 20110275944A1
• Time in Patent Office: 1,811 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/0225 the pressure being controlled by electric signals, e.g. derived from Korotkoff sounds
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7253 characterised by using transforms
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: G16H 10/40 for data related to laboratory analysis, e.g. patient specimen analysis
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass

Abstract

A method for determining a calibrated aortic pressure waveform from a brachial cuff waveform involves the use of one or more generalized transfer functions. The one or more generalized transfer functions are specific for predetermined brachial cuff pressure ranges, such as below diastolic pressure, between diastolic and systolic pressure, and above systolic pressure. The brachial cuff is inflated to a pressure within the pressure range appropriate for the generalized transfer function to be applied to the brachial cuff waveform to generate the aortic pressure waveform. In some circumstances, it may be necessary to use a calibration transfer function to generate a calibrated aortic waveform. In other circumstances, the calibration transfer function is not necessary.

Claims

1. In a blood pressure measuring system, a method for determining a calibrated aortic pressure waveform, the method comprising the steps:

providing an inflatable brachial cuff having a pressure sensor to measure pressure within the brachial cuff, said pressure sensor outputting an analog signal;

providing a digital signal processor that receives the analog signal from the pressure sensor and outputs a digital brachial cuff signal containing data to record the patient'"'"'s brachial cuff waveform;

measuring at least the patient'"'"'s brachial systolic pressure (SP) and brachial diastolic pressure (DP) using the brachial cuff in an oscillometric mode;

inflating the brachial cuff around a patient'"'"'s upper arm to a constant pressure that is less than the measured DP;

maintaining the brachial cuff at said constant pressure to record the patient'"'"'s brachial cuff waveform, wherein the brachial cuff waveform is a volumetric displacement waveform;

using at least two of brachial systolic pressure (SP), brachial mean pressure (MP) and brachial diastolic pressure (DP) to calibrate the brachial cuff waveform, wherein brachial mean pressure (MP) if used is determined from the measured brachial systolic pressure (SP) and the measured brachial diastolic pressure (DP); and

using one or more generalized transfer functions to convert the calibrated brachial cuff waveform to a calibrated aortic pressure waveform, wherein said one or more generalized transfer functions represent the harmonic ratio in amplitude and phase to transform the calibrated brachial cuff volumetric displacement waveform to the calibrated aortic pressure waveform when the brachial cuff is inflated to a pressure less than the patient'"'"'s measured diastolic pressure (DP).

2. A method of determining a calibrated aortic pressure waveform as recited in claim 1 further comprising the step of using a generalized calibration transfer function when converting the calibrated brachial cuff waveform to a calibrated aortic pressure waveform.

3. A method as recited in claim 1 further comprising the step of displaying the calibrated aortic pressure waveform as a trace or otherwise on a computer display screen.

4. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the one or more generalized transfer functions includes a generalized transfer function that transforms the calibrated brachial cuff waveform directly to an aortic pressure waveform.

5. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein one or more generalized transfer functions comprise at least:

a first generalized transfer function that mathematically transforms the calibrated brachial cuff waveform to an intermediate artery pressure waveform and a second generalized transfer function that transforms the intermediate artery pressure waveform to an aortic pressure waveform.

6. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the brachial cuff is inflated around the patient'"'"'s upper arm to a constant pressure that is between 10-90% of the measured diastolic pressure (DP).

7. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the one or more generalized transfer functions are estimated from simultaneously recorded data for a general population.

8. A method for determining a calibrated aortic pressure waveform as recited in claim 1 wherein the one or more generalized transfer functions operate in the frequency domain.

9. A method for determining a calibrated aortic pressure waveform as recited in claim 1 wherein the one or more generalized transfer functions operate in the time domain.

10. A method for determining a calibrated aortic pressure waveform as recited in claim 1 wherein at least one of the one or more generalized transfer functions are embodied in a filter.

11. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the brachial cuff is part of a device that comprises the brachial cuff, a tube, a pressure pump with a pressure control system, and a pressure sensor that provides an analog signal and the blood pressure measuring system further comprises the digital signal processor that has a low pass filter and a high pass filter, receives the analog signal from the pressure sensor and outputs a digital brachial cuff signal containing filtered data preserving the features of patient'"'"'s brachial cuff volumetric displacement waveform, and a computer that receives the digital brachial cuff signal, records and calibrates the brachial cuff waveform, and converts the calibrated brachial cuff waveform to the calibrated aortic pressure waveform using said one or more generalized transfer functions representing the harmonic ratio in amplitude and phase to transform the calibrated brachial cuff volumetric displacement waveform to the calibrated aortic pressure waveform when the brachial cuff is inflated to a pressure less than the patient'"'"'s measured diastolic pressure (DP).

12. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the digital signal processor has a low pass filter and a high pass filter and outputs a digital brachial cuff signal containing a filtered data that preserves waveform features of the patient'"'"'s brachial cuff volumetric displacement waveform.

13. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the one or more generalized transfer functions are implemented by software on a computer.

14. In a blood pressure measuring system, a method for determining a calibrated aortic pressure waveform, the method comprising the steps:

providing an inflatable brachial cuff having a pressure sensor to measure pressure within the brachial cuff, said pressure sensor outputting an analog signal;

providing a digital signal processor that receives the analog signal from the pressure sensor and outputs a digital brachial cuff signal containing data to record the patient'"'"'s brachial cuff waveform;

measuring at least the patient'"'"'s brachial systolic pressure (SP) and brachial diastolic pressure (DP) using the brachial cuff in an oscillometric mode;

inflating the brachial cuff around a patient'"'"'s upper arm to a constant pressure that is above the measured SP;

maintaining the brachial cuff at said constant pressure to record the patient'"'"'s brachial cuff waveform, wherein the brachial cuff waveform is a volumetric displacement waveform;

using at least two of brachial systolic pressure (SP), brachial mean pressure (MP) and brachial diastolic pressure (DP) to calibrate the brachial cuff waveform, wherein brachial mean pressure (MP), if used, is determined from the measured brachial systolic pressure (SP) and the measured brachial diastolic pressure (DP); and

using one or more generalized transfer functions to convert the calibrated brachial cuff waveform to a calibrated aortic pressure waveform, wherein said one or more generalized transfer functions represent the harmonic ratio in amplitude and phase to transform the calibrated brachial cuff volumetric displacement waveform to the calibrated aortic pressure waveform when the brachial cuff is inflated to a pressure above the patient'"'"'s measured systolic pressure (SP).

15. A method of determining a calibrated aortic pressure waveform as recited in claim 14 further comprising the step of using a generalized calibration transfer function when converting the calibrated brachial cuff waveform to a calibrated aortic pressure waveform.

16. A method as recited in claim 14 further comprising the step of displaying the calibrated aortic pressure waveform as a trace or otherwise on a computer display screen.

17. A method of determining a calibrated aortic pressure waveform as recited in claim 14 wherein the one or more generalized transfer functions includes a generalized transfer function that transforms the calibrated brachial cuff waveform directly to an aortic pressure waveform.

18. A method of determining a calibrated aortic pressure waveform as recited in claim 14 wherein one or more generalized transfer functions comprise at least:

a first generalized transfer function that mathematically transforms the calibrated brachial cuff waveform to an intermediate artery pressure waveform and a second generalized transfer function that transforms the intermediate artery pressure waveform to an aortic pressure waveform.

19. A method of determining a calibrated aortic pressure waveform as recited in claim 14 wherein the brachial cuff is inflated around the patient'"'"'s upper arm to a constant pressure that is in the following range:

P_Cuff=[(K%)+1]SP_B

where K % ranges from 10% to 90%.

20. A method of determining a calibrated aortic pressure waveform as recited in claim 14 wherein the one or more generalized transfer functions are estimated from simultaneously recorded data for a general population.

21. A method for determining a calibrated aortic pressure waveform as recited in claim 14 wherein the one or more generalized transfer functions operate in the frequency domain.

22. A method for determining a calibrated aortic pressure waveform as recited in claim 14 wherein the one or more generalized transfer functions operate in the time domain.

23. A method for determining a calibrated aortic pressure waveform as recited in claim 14 wherein at least one of the one or more generalized transfer functions are embodied in a filter.

24. A method of determining a calibrated aortic pressure waveform as recited in claim 14 wherein the brachial cuff is part of a device that comprises the brachial cuff, a tube, a pressure pump with a pressure control system, and a pressure sensor that provides an analog signal and the blood pressure measuring system further comprises the digital signal processor that has a low pass filter and a high pass filter, receives the analog signal from the pressure sensor and outputs a digital brachial cuff signal containing filtered data preserving the features of patient'"'"'s brachial cuff volumetric displacement waveform, and a computer that receives the digital brachial cuff signal, records and calibrates the brachial cuff waveform, and converts the calibrated brachial cuff waveform to the calibrated aortic pressure waveform using said one or more generalized transfer functions representing the harmonic ratio in amplitude and phase to transform the calibrated brachial cuff volumetric displacement waveform to the calibrated aortic pressure waveform when the brachial cuff is inflated to a pressure above the patient'"'"'s measured systolic pressure (SP).

25. A method of determining a calibrated aortic pressure waveform as recited in claim 14 wherein the digital signal processor has a low pass filter and a high pass filter and outputs a digital brachial cuff signal containing a filtered data that preserves waveform features of the patient'"'"'s brachial cuff volumetric displacement waveform.

26. A method of determining a calibrated aortic pressure waveform as recited in claim 14 wherein the one or more generalized transfer functions are implemented by software on a computer.